Here are a few of my DIY projects for the system.
The first is the closed loop I built for circulating water. The pipe is 1" and running on a Little Giant 2 that I had laying around.
The tall riser is unscrewable to prime the pump initially with water. That has been the only time I've needed to take that cap off, even after power outages. The design incorporates dozens of 1/8" holes along a 5" length of 1" pvc for an intake. This feature keeps snails, fish, nudibranchs or even cukes from getting stuck to the intake and perishing.
This next one is a Calcium reactor built by a friend of mine which now runs my whole system (~125 gallons). It uses a 4" diameter pvc pipe, ~30" tall. It features a passive intake line from my return pump, re-circulates using a Mag2 pump, and can hold about 5# of media (which has lasted me 7 months so far on this SPS system). It also has an acrylic window for monitoring media.